Photorealistic Graphics Display:
Computer Graphics Displayphotorealistic imagemethod andcamera to take picturesVery similar
In computer graphics:
setting up a camera is equivalent toselect viewpoint, the selection scenario is equivalent toDetermine the extent of the graphic display, taking a picture equivalent toGraphics Transformation and Perspective Projection, developing the photo is equivalent toscreen display
1. Local coordinate system (User coordinate system Local Coordinate System)
Definition method:
Each object in the scene has its own local coordinate system. For example, when we build a cube, we often put the origin of the local coordinate system on the body center or a vertex of the cube.
effect:
It is used to construct the positional relationship between objects.
2. World Coordinate System
Definition method:
It can be understood as the global coordinate system of the entire scene.
effect:
It is used to describe the positional relationship between objects and is generally defined as a right-handed system.
3. Observation coordinate system (viewing coordinate system Viewing Coordinate System)
Definition method:
The position of the viewpoint is taken as the origin , the line of sight direction (or the opposite direction) is the z-axis , the y-axis is defined by an upward viewing vector defined by the user , and the x-axis is determined by cross product .
effect:
It is used to specify the output range of the graphics , reposition and describe the objects in the entire world coordinate system from the perspective of the observer, thus simplifying the mathematical derivation and calculation of the imaging of geometric objects on the projection plane.
4. Imaging plane coordinate system (projected coordinate system)
Definition method:
A two-dimensional coordinate system generally defines the imaging plane by specifying the distance between the imaging plane and the viewpoint, and can further define the imaging plane namedwindowThe square area to achieve partial imaging.
effect:
Specify all points of the object on the imaging plane .
5. Screen coordinate system (Device Coordinates)
Definition method:
A coordinate system relative to a graphics display device. Such as the coordinate system of a monitor or a printer.
The origin is located at the upper left corner of the client area of the screen, the x-axis is positive horizontally, the y-axis is positive vertically downward, and the basic unit is pixel.
When the imaging window is defined, it can be further defined in the screen coordinate system namedview areaThe bounded area of , the imaging in the view is what can actually be observed.
effect:
The definition of points on the surface of some special computer graphics display devices (such as raster displays).
6. Summary:
In short, in order to create and display geometric objects in three-dimensional space, the world coordinate system must be established first . Then, it is necessary to specify the orientation of the viewpoint, the orientation of the line of sight and the imaging plane, and define the observation coordinate system . In order to observe the imaging of the object, it is necessary to carry out the projection transformation after the transformation of each coordinate system to obtain the imaging of the object .